Craig Stephen Hicks – who was charged on Wednesday with three counts of first-degree murder in connection with the shooting deaths of Deah Barakat, 23, his wife Yusor Mohammad Abu-Salha, 21, and her sister Razan Mohammad Abu-Salha, 19 – was feared by his neighbours.

The information that has trickled out about the 46-year-old paints him as a second amendment advocate who had a concealed weapons permit and who argued often with his neighbors over parking and loud noises; posted online about his disdain for religion – all religions – and had in past years obsessively watched a film about a disgruntled man who goes on a shooting rampage.

Chapel Hill police said the killings may have stemmed from an ongoing dispute over parking, a constant inconvenience for residents of Finley Forest.

But the family feels strongly that what transpired on Tuesday night was not the escalation of a confrontation between neighbours, but a hate crime perpetrated in cold blood against the three students because they were Muslim.

“There were several incidents involving him harassing and threatening my brother,” Farris Barakat told the Guardian, adding that Hicks had come to their apartment at least four times, and that in the more recent visits he had “pulled his jacket to show his gun, almost like brandishing it”.

Farris said that Yusor and Deah had been afraid of Hicks, and that they had previously discussed reporting him to the police, and that both Yusor and her mother – who wore headscarfs – had sensed hostility from him based on their religious attire.

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Barakat’s comments echo those of Mohammad Abu-Salha, the father of the two women killed.

“This man had picked on my daughter and her husband a couple of times before, and he talked with them with his gun in his belt,” Abu-Salha said. “And they were uncomfortable with him, but they did not know he would go this far.”

Hicks’s social media accounts depict a man who appears to be philosophically opposed to religion in all its forms. On Facebook, Hicks describes himself under political views as a “gun-toting liberal” and an “anti-theist”. The banner photo at the top of the page says: “Of course I want religion to go away.”

Under the “religion” section of his Facebook page is a lengthy rant. “I give your religion as much respect as your religion gives me,” he begins. “There’s nothing complicated about it, and I have every right to insult a religion that goes out of its way to insult, to judge, and to condemn me as an inadequate human being – which your religion does with self-righteous gusto.”

But on Wednesday, Hicks’s wife, Karen, told the Associated Press that religion wasn’t the motive for her husband’s attack. At a press conference later that day, her attorney suggested that a mental illness may have precipitated the attack.

“Obviously it’s not within the range of normal behavior for someone to shoot three people over parking issues,” Karen Hicks’s attorney, Robert Maitland, said during the press conference. He declined to provide further details.

Neighbors say Hicks was an angry, confrontational man who constantly harangued residents about where they parked their car and the noise level at the condominium complex where they lived.

Samantha Maness, a 25-year-old student who lived in the condominium complex, told the Raleigh News and Observer that Hicks was equally hostile with all the residents, and didn’t appear to target anyone based on their religion.

“He was aggressive toward a lot of people in the community,” Maness told the paper. “He had equal-opportunity anger toward a lot of the residents here.”

Craig Stephen Hicks, 46, who was arrested on three counts of murder early on Wednesday. Photograph: Zuma/Rex

Maness said the situation reached a boiling point last year, prompting residents to call a meeting in the complex’s clubhouse about his behaviour, which she said made them feel “unsafe and uncomfortable”.

Meanwhile, Hicks’ ex-wife told the AP that his favorite film was Falling Down, made in 1993 and starring Michael Douglas as an out-of-work engineer who goes on a shooting rampage.

“That always freaked me out,” Cynthia Hurley, who divorced Hicks about 17 years ago, told the wire service. “He watched it incessantly. He thought it was hilarious. He had no compassion at all.”

Both local and federal officials acknowledged widespread concern that the violence was motivated bythe victims’ faith, but urged the communityto reserve judgment and give investigators time to examine the case.

Speaking during a press conference on Wednesday, US district attorney Ripley Rand said it appears the killings are “not part of a targeted campaign against Muslims in North Carolina”. The investigation is still in the hands of local law enforcement, but Rand said federal officials are watching closely.

“This appears at this point to have been an isolated incident,” he said.

Invoking the hashtag #MuslimLivesMatter, which sprung up on Twitter after the attack, Chapel Hill’s mayor sought to calm residents, calling the killings an “incomprehensible loss”.

“I share strong feelings of outrage and shock with my fellow citizens and university students – as well as concerned people everywhere,” said Mark Kleinschmidt, the mayor. “We do not know whether anti-Muslim bias played a role in this crime, but I do recognise the fear that members of our community may feel. Chapel Hill is a place for everyone, a place where Muslim lives matter.